Evaluation of radiolabeled acetate and fluoroacetate as PET tracers of cerebral oxidative metabolism

The authors have investigated the potential use of radiolabeled acetate (ACE) and fluoroacetate (FACE) as tracers of cerebral oxidative (Krebs cycle) metabolism. The rates of accumulation of FACE and ACE were compared with simultaneously measured, fluorodeoxyglucose (FDG)-based, glucose metabolic rates in awake rats with dual-tracer quantitative digital autoradiography. Both FACE and ACE crossed the blood-brain barrier at approximately the same rate as glucose. Metabolism of FACE by the brain, however, was extremely slow; metabolites were undetectable above background levels through 60 minutes. On the other hand, metabolic uptake of ACE by the brain was significant, averaging 70%--80% of the glucose metabolic rate. While the metabolic images of ACE were similar to those of FDG, variations in the uptake patterns of FDG and ACE occurred in some structures, perhaps related to regional variations in glucose versus oxygen metabolism